Hydrogeochemical characteristics of fluoride in groundwater: a case study in Yuncheng Basin,Northern China

摘要

Yuncheng Basin of Shanxi province in northern China is one of the typical endemic fluorosis areas caused by drinking water for many years. This study investigated the relationship between hydrogeochemical fades and the fluoride concentration in the groundwater in Yuncheng Basin. Piper diagram was used to determine the groundwater hydrogeochemical fades. Mean of groundwater fluoride concentration was carried out according to different hydrogeochemical facies. The result suggested that groundwater with lowest fluorine content belong to SO4-Ca water, and then is HCO3-Ca, HCO3-Ca-Na and HCO3-Na-Mg water, while the HCO3-Na water with low TDS commonly had higher fluoride content. SO4-Cl-Na, SO4-Na and SO4-HCO3-Na water with high fluoride content were observed on the north bank of the salt lake. Geochemical modeling using PHREEQC show that increased NaHCO3 accelerated the further dissolution of fluorite by the consumption of Ca2- as Ca(HCO3)+; and the fluorine content elevation in Cl-Na/SO4-Na water mostly dependent on the decrease of ion activity of Ca2+ and F-with the an increase of ion strength, which causes the further dissolution of fluorite.